中文摘要：

有色溶解有机物（CDOM）是海洋溶解有机碳（DOC）的重要组成成分，其光降解能加速海草床生源物质和能量的流动。本文以海南新村湾海草床CDOM为研究对象，研究CDOM的空间分布特征，分析其主要来源，并结合光降解实验，探讨CDOM在紫外光（uV．B）照射下内部物质组分的变化过程。结果表明：新村湾冬季CDOM的分布主要表现为海草区最高，河口区域和网箱养殖区次之，而海湾中心最低；海草区和河口区CDOM的类蛋白质与类腐殖质荧光强度比网箱养殖区高；海草区和河流区域的CDOM分子量较大，而网箱养殖区的CDOM分子量较小；CDOM在UV—B下暴露5d，海草区域、河口区域和网箱养殖区的类蛋白质荧光强度分别下降了44．67％、31．75％和37．09％，表明海草区域类蛋白质吸收了大部分UV—B，降解速率比其他区域快；而类腐殖质荧光强度的下降比例分别为43．64％、36．32％和50．18％，网箱养殖区CDOM的类腐殖质下降速率较快，这可能是由于网箱养殖区的CDOM分子量小，结构简单，易在UV—B照射下降解。因此，海草床海草的释放、河流的输入及网箱养殖区浮游植物的降解是新村湾的CDOM主要来源。

英文摘要：

Chromophoric dissolved organic matter （CDOM） is an important dissolved organic carbon reservoir in marine systems. Photodegradation of CDOM can accelerate recycling of nutri- ents and refractory organic matters. To examine the spatial distribution and sources of CDOM in seagrass bed in Xineun Bay, Hainan Island, the absorption coefficient [ a（ 355 ）] and exponen- tial slope value （S） were investigated in this region. The processes of the photo degradation of CDOM were also studied in the laboratory experiment. The results showed that the value of a（355） was highest in seagrass bed in the southern bay, followed by the small river mouth and cage-farming area, and then the center of the bay. The fluorescence intensities at 280 nm excita- tion [ Fn（280）] and 350 nm excitation [ Fn （355）] in protein-like and humic-like substances were higher in the seagrass bed and river mouth than in the cage-farming area. These results indi- cated that the molecular weight of CDOM in the seagrass bed and the river mouth area were high-er than that of CDOM released by phytoplankton degradation in the cage-farming area. In labora- tory, after exposure to UV-B for five days, the protein-like substances of CDOM from the seagrass bed, river mouth, and cage-farming area decreased by 44.67%, 31.75% and 37.09%, respec- tively, indicating that protein-like substances in the seagrass bed absorbed UV-B more efficiently. The humic-like substances decreased by 43.64%, 36.32%, and 50.18%, respectively, which suggested the smaller molecular weight of CDOM from the cage-farming area could be degraded more easily under UV-B. Therefore, our study revealed that seagrass release, riverine inputs, and degradation from phytoplankton in cage-farming areas were the main sources of CDOM in Xincun Bay.